1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/shared/workgroup.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/atomic.inline.hpp"
30 #include "runtime/os.hpp"
31
32 // Definitions of WorkGang methods.
33
34 AbstractWorkGang::AbstractWorkGang(const char* name,
35 bool are_GC_task_threads,
36 bool are_ConcurrentGC_threads) :
37 _name(name),
38 _are_GC_task_threads(are_GC_task_threads),
39 _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
40
41 assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
42 "They cannot both be STW GC and Concurrent threads" );
43
44 // Other initialization.
45 _monitor = new Monitor(/* priority */ Mutex::leaf,
46 /* name */ "WorkGroup monitor",
47 /* allow_vm_block */ are_GC_task_threads,
48 Monitor::_safepoint_check_sometimes);
49 assert(monitor() != NULL, "Failed to allocate monitor");
50 _terminate = false;
51 _task = NULL;
52 _sequence_number = 0;
53 _started_workers = 0;
54 _finished_workers = 0;
55 }
56
57 WorkGang::WorkGang(const char* name,
58 uint workers,
59 bool are_GC_task_threads,
60 bool are_ConcurrentGC_threads) :
61 AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {
62 _total_workers = workers;
63 }
64
65 GangWorker* WorkGang::allocate_worker(uint which) {
66 GangWorker* new_worker = new GangWorker(this, which);
67 return new_worker;
68 }
69
70 // The current implementation will exit if the allocation
71 // of any worker fails. Still, return a boolean so that
72 // a future implementation can possibly do a partial
73 // initialization of the workers and report such to the
74 // caller.
75 bool WorkGang::initialize_workers() {
76
77 if (TraceWorkGang) {
78 tty->print_cr("Constructing work gang %s with %d threads",
79 name(),
80 total_workers());
81 }
82 _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers(), mtInternal);
83 if (gang_workers() == NULL) {
84 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "Cannot create GangWorker array.");
85 return false;
86 }
87 os::ThreadType worker_type;
88 if (are_ConcurrentGC_threads()) {
89 worker_type = os::cgc_thread;
90 } else {
91 worker_type = os::pgc_thread;
92 }
93 for (uint worker = 0; worker < total_workers(); worker += 1) {
94 GangWorker* new_worker = allocate_worker(worker);
95 assert(new_worker != NULL, "Failed to allocate GangWorker");
96 _gang_workers[worker] = new_worker;
97 if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
98 vm_exit_out_of_memory(0, OOM_MALLOC_ERROR,
99 "Cannot create worker GC thread. Out of system resources.");
100 return false;
101 }
102 if (!DisableStartThread) {
103 os::start_thread(new_worker);
104 }
105 }
106 return true;
107 }
108
109 AbstractWorkGang::~AbstractWorkGang() {
110 if (TraceWorkGang) {
111 tty->print_cr("Destructing work gang %s", name());
112 }
113 stop(); // stop all the workers
114 for (uint worker = 0; worker < total_workers(); worker += 1) {
115 delete gang_worker(worker);
116 }
117 delete gang_workers();
118 delete monitor();
119 }
120
121 GangWorker* AbstractWorkGang::gang_worker(uint i) const {
122 // Array index bounds checking.
123 GangWorker* result = NULL;
124 assert(gang_workers() != NULL, "No workers for indexing");
125 assert(i < total_workers(), "Worker index out of bounds");
126 result = _gang_workers[i];
127 assert(result != NULL, "Indexing to null worker");
128 return result;
129 }
130
131 void WorkGang::run_task(AbstractGangTask* task) {
132 run_task(task, total_workers());
133 }
134
135 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
136 task->set_for_termination(no_of_parallel_workers);
137
138 // This thread is executed by the VM thread which does not block
139 // on ordinary MutexLocker's.
140 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
141 if (TraceWorkGang) {
142 tty->print_cr("Running work gang %s task %s", name(), task->name());
143 }
144 // Tell all the workers to run a task.
145 assert(task != NULL, "Running a null task");
146 // Initialize.
147 _task = task;
148 _sequence_number += 1;
149 _started_workers = 0;
150 _finished_workers = 0;
151 // Tell the workers to get to work.
152 monitor()->notify_all();
153 // Wait for them to be finished
154 while (finished_workers() < no_of_parallel_workers) {
155 if (TraceWorkGang) {
156 tty->print_cr("Waiting in work gang %s: %u/%u finished sequence %d",
157 name(), finished_workers(), no_of_parallel_workers,
158 _sequence_number);
159 }
160 monitor()->wait(/* no_safepoint_check */ true);
161 }
162 _task = NULL;
163 if (TraceWorkGang) {
164 tty->print_cr("\nFinished work gang %s: %u/%u sequence %d",
165 name(), finished_workers(), no_of_parallel_workers,
166 _sequence_number);
167 Thread* me = Thread::current();
168 tty->print_cr(" T: " PTR_FORMAT " VM_thread: %d", p2i(me), me->is_VM_thread());
169 }
170 }
171
172 void FlexibleWorkGang::run_task(AbstractGangTask* task) {
173 // If active_workers() is passed, _finished_workers
174 // must only be incremented for workers that find non_null
175 // work (as opposed to all those that just check that the
176 // task is not null).
177 WorkGang::run_task(task, (uint) active_workers());
178 }
179
180 void AbstractWorkGang::stop() {
181 // Tell all workers to terminate, then wait for them to become inactive.
182 MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
183 if (TraceWorkGang) {
184 tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
185 }
186 _task = NULL;
187 _terminate = true;
188 monitor()->notify_all();
189 while (finished_workers() < active_workers()) {
190 if (TraceWorkGang) {
191 tty->print_cr("Waiting in work gang %s: %u/%u finished",
192 name(), finished_workers(), active_workers());
193 }
194 monitor()->wait(/* no_safepoint_check */ true);
195 }
196 }
197
198 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
199 assert(monitor()->owned_by_self(), "worker_poll is an internal method");
200 assert(data != NULL, "worker data is null");
201 data->set_terminate(terminate());
202 data->set_task(task());
203 data->set_sequence_number(sequence_number());
204 }
205
206 void AbstractWorkGang::internal_note_start() {
207 assert(monitor()->owned_by_self(), "note_finish is an internal method");
208 _started_workers += 1;
209 }
210
211 void AbstractWorkGang::internal_note_finish() {
212 assert(monitor()->owned_by_self(), "note_finish is an internal method");
213 _finished_workers += 1;
214 }
215
216 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
217 uint num_thr = total_workers();
218 for (uint i = 0; i < num_thr; i++) {
219 gang_worker(i)->print_on(st);
220 st->cr();
221 }
222 }
223
224 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
225 assert(tc != NULL, "Null ThreadClosure");
226 uint num_thr = total_workers();
227 for (uint i = 0; i < num_thr; i++) {
228 tc->do_thread(gang_worker(i));
229 }
230 }
231
232 // GangWorker methods.
233
234 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
235 _gang = gang;
236 set_id(id);
237 set_name("%s#%d", gang->name(), id);
238 }
239
240 void GangWorker::run() {
241 initialize();
242 loop();
243 }
244
245 void GangWorker::initialize() {
246 this->initialize_thread_local_storage();
247 this->record_stack_base_and_size();
248 this->initialize_named_thread();
249 assert(_gang != NULL, "No gang to run in");
250 os::set_priority(this, NearMaxPriority);
251 if (TraceWorkGang) {
252 tty->print_cr("Running gang worker for gang %s id %u",
253 gang()->name(), id());
254 }
255 // The VM thread should not execute here because MutexLocker's are used
256 // as (opposed to MutexLockerEx's).
257 assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
258 " of a work gang");
259 }
260
261 void GangWorker::loop() {
262 int previous_sequence_number = 0;
263 Monitor* gang_monitor = gang()->monitor();
264 for ( ; /* !terminate() */; ) {
265 WorkData data;
266 int part; // Initialized below.
267 {
268 // Grab the gang mutex.
269 MutexLocker ml(gang_monitor);
270 // Wait for something to do.
271 // Polling outside the while { wait } avoids missed notifies
272 // in the outer loop.
273 gang()->internal_worker_poll(&data);
274 if (TraceWorkGang) {
275 tty->print("Polled outside for work in gang %s worker %u",
276 gang()->name(), id());
277 tty->print(" terminate: %s",
278 data.terminate() ? "true" : "false");
279 tty->print(" sequence: %d (prev: %d)",
280 data.sequence_number(), previous_sequence_number);
281 if (data.task() != NULL) {
282 tty->print(" task: %s", data.task()->name());
283 } else {
284 tty->print(" task: NULL");
285 }
286 tty->cr();
287 }
288 for ( ; /* break or return */; ) {
289 // Terminate if requested.
290 if (data.terminate()) {
291 gang()->internal_note_finish();
292 gang_monitor->notify_all();
293 return;
294 }
295 // Check for new work.
296 if ((data.task() != NULL) &&
297 (data.sequence_number() != previous_sequence_number)) {
298 if (gang()->needs_more_workers()) {
299 gang()->internal_note_start();
300 gang_monitor->notify_all();
301 part = gang()->started_workers() - 1;
302 break;
303 }
304 }
305 // Nothing to do.
306 gang_monitor->wait(/* no_safepoint_check */ true);
307 gang()->internal_worker_poll(&data);
308 if (TraceWorkGang) {
309 tty->print("Polled inside for work in gang %s worker %u",
310 gang()->name(), id());
311 tty->print(" terminate: %s",
312 data.terminate() ? "true" : "false");
313 tty->print(" sequence: %d (prev: %d)",
314 data.sequence_number(), previous_sequence_number);
315 if (data.task() != NULL) {
316 tty->print(" task: %s", data.task()->name());
317 } else {
318 tty->print(" task: NULL");
319 }
320 tty->cr();
321 }
322 }
323 // Drop gang mutex.
324 }
325 if (TraceWorkGang) {
326 tty->print("Work for work gang %s id %u task %s part %d",
327 gang()->name(), id(), data.task()->name(), part);
328 }
329 assert(data.task() != NULL, "Got null task");
330 data.task()->work(part);
331 {
332 if (TraceWorkGang) {
333 tty->print("Finish for work gang %s id %u task %s part %d",
334 gang()->name(), id(), data.task()->name(), part);
335 }
336 // Grab the gang mutex.
337 MutexLocker ml(gang_monitor);
338 gang()->internal_note_finish();
339 // Tell the gang you are done.
340 gang_monitor->notify_all();
341 // Drop the gang mutex.
342 }
343 previous_sequence_number = data.sequence_number();
344 }
345 }
346
347 bool GangWorker::is_GC_task_thread() const {
348 return gang()->are_GC_task_threads();
349 }
350
351 bool GangWorker::is_ConcurrentGC_thread() const {
352 return gang()->are_ConcurrentGC_threads();
353 }
354
355 void GangWorker::print_on(outputStream* st) const {
356 st->print("\"%s\" ", name());
357 Thread::print_on(st);
358 st->cr();
359 }
360
361 // Printing methods
362
363 const char* AbstractWorkGang::name() const {
364 return _name;
365 }
366
367 #ifndef PRODUCT
368
369 const char* AbstractGangTask::name() const {
370 return _name;
371 }
372
373 #endif /* PRODUCT */
374
375 // FlexibleWorkGang
376
377
378 // *** WorkGangBarrierSync
379
380 WorkGangBarrierSync::WorkGangBarrierSync()
381 : _monitor(Mutex::safepoint, "work gang barrier sync", true,
382 Monitor::_safepoint_check_never),
383 _n_workers(0), _n_completed(0), _should_reset(false), _aborted(false) {
384 }
385
386 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
387 : _monitor(Mutex::safepoint, name, true, Monitor::_safepoint_check_never),
388 _n_workers(n_workers), _n_completed(0), _should_reset(false), _aborted(false) {
389 }
390
391 void WorkGangBarrierSync::set_n_workers(uint n_workers) {
392 _n_workers = n_workers;
393 _n_completed = 0;
394 _should_reset = false;
395 _aborted = false;
396 }
397
398 bool WorkGangBarrierSync::enter() {
399 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
400 if (should_reset()) {
401 // The should_reset() was set and we are the first worker to enter
402 // the sync barrier. We will zero the n_completed() count which
403 // effectively resets the barrier.
404 zero_completed();
405 set_should_reset(false);
406 }
407 inc_completed();
408 if (n_completed() == n_workers()) {
409 // At this point we would like to reset the barrier to be ready in
410 // case it is used again. However, we cannot set n_completed() to
411 // 0, even after the notify_all(), given that some other workers
412 // might still be waiting for n_completed() to become ==
413 // n_workers(). So, if we set n_completed() to 0, those workers
414 // will get stuck (as they will wake up, see that n_completed() !=
415 // n_workers() and go back to sleep). Instead, we raise the
416 // should_reset() flag and the barrier will be reset the first
417 // time a worker enters it again.
418 set_should_reset(true);
419 monitor()->notify_all();
420 } else {
421 while (n_completed() != n_workers() && !aborted()) {
422 monitor()->wait(/* no_safepoint_check */ true);
423 }
424 }
425 return !aborted();
426 }
427
428 void WorkGangBarrierSync::abort() {
429 MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
430 set_aborted();
431 monitor()->notify_all();
432 }
433
434 // SubTasksDone functions.
435
436 SubTasksDone::SubTasksDone(uint n) :
437 _n_tasks(n), _tasks(NULL) {
438 _tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
439 guarantee(_tasks != NULL, "alloc failure");
440 clear();
441 }
442
443 bool SubTasksDone::valid() {
444 return _tasks != NULL;
445 }
446
447 void SubTasksDone::clear() {
448 for (uint i = 0; i < _n_tasks; i++) {
449 _tasks[i] = 0;
450 }
451 _threads_completed = 0;
452 #ifdef ASSERT
453 _claimed = 0;
454 #endif
455 }
456
457 bool SubTasksDone::is_task_claimed(uint t) {
458 assert(t < _n_tasks, "bad task id.");
459 uint old = _tasks[t];
460 if (old == 0) {
461 old = Atomic::cmpxchg(1, &_tasks[t], 0);
462 }
463 assert(_tasks[t] == 1, "What else?");
464 bool res = old != 0;
465 #ifdef ASSERT
466 if (!res) {
467 assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
468 Atomic::inc((volatile jint*) &_claimed);
469 }
470 #endif
471 return res;
472 }
473
474 void SubTasksDone::all_tasks_completed(uint n_threads) {
475 jint observed = _threads_completed;
476 jint old;
477 do {
478 old = observed;
479 observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
480 } while (observed != old);
481 // If this was the last thread checking in, clear the tasks.
482 uint adjusted_thread_count = (n_threads == 0 ? 1 : n_threads);
483 if (observed + 1 == (jint)adjusted_thread_count) {
484 clear();
485 }
486 }
487
488
489 SubTasksDone::~SubTasksDone() {
490 if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);
491 }
492
493 // *** SequentialSubTasksDone
494
495 void SequentialSubTasksDone::clear() {
496 _n_tasks = _n_claimed = 0;
497 _n_threads = _n_completed = 0;
498 }
499
500 bool SequentialSubTasksDone::valid() {
501 return _n_threads > 0;
502 }
503
504 bool SequentialSubTasksDone::is_task_claimed(uint& t) {
505 uint* n_claimed_ptr = &_n_claimed;
506 t = *n_claimed_ptr;
507 while (t < _n_tasks) {
508 jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
509 if (res == (jint)t) {
510 return false;
511 }
512 t = *n_claimed_ptr;
513 }
514 return true;
515 }
516
517 bool SequentialSubTasksDone::all_tasks_completed() {
518 uint* n_completed_ptr = &_n_completed;
519 uint complete = *n_completed_ptr;
520 while (true) {
521 uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
522 if (res == complete) {
523 break;
524 }
525 complete = res;
526 }
527 if (complete+1 == _n_threads) {
528 clear();
529 return true;
530 }
531 return false;
532 }
533
534 bool FreeIdSet::_stat_init = false;
535 FreeIdSet* FreeIdSet::_sets[NSets];
536 bool FreeIdSet::_safepoint;
537
538 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
539 _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
540 {
541 _ids = NEW_C_HEAP_ARRAY(int, sz, mtInternal);
542 for (int i = 0; i < sz; i++) _ids[i] = i+1;
543 _ids[sz-1] = end_of_list; // end of list.
544 if (_stat_init) {
545 for (int j = 0; j < NSets; j++) _sets[j] = NULL;
546 _stat_init = true;
547 }
548 // Add to sets. (This should happen while the system is still single-threaded.)
549 for (int j = 0; j < NSets; j++) {
550 if (_sets[j] == NULL) {
551 _sets[j] = this;
552 _index = j;
553 break;
554 }
555 }
556 guarantee(_index != -1, "Too many FreeIdSets in use!");
557 }
558
559 FreeIdSet::~FreeIdSet() {
560 _sets[_index] = NULL;
561 FREE_C_HEAP_ARRAY(int, _ids);
562 }
563
564 void FreeIdSet::set_safepoint(bool b) {
565 _safepoint = b;
566 if (b) {
567 for (int j = 0; j < NSets; j++) {
568 if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
569 Monitor* mon = _sets[j]->_mon;
570 mon->lock_without_safepoint_check();
571 mon->notify_all();
572 mon->unlock();
573 }
574 }
575 }
576 }
577
578 #define FID_STATS 0
579
580 int FreeIdSet::claim_par_id() {
581 #if FID_STATS
582 thread_t tslf = thr_self();
583 tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
584 #endif
585 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
586 while (!_safepoint && _hd == end_of_list) {
587 _waiters++;
588 #if FID_STATS
589 if (_waiters > 5) {
590 tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
591 tslf, _waiters, _claimed);
592 }
593 #endif
594 _mon->wait(Mutex::_no_safepoint_check_flag);
595 _waiters--;
596 }
597 if (_hd == end_of_list) {
598 #if FID_STATS
599 tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
600 #endif
601 return -1;
602 } else {
603 int res = _hd;
604 _hd = _ids[res];
605 _ids[res] = claimed; // For debugging.
606 _claimed++;
607 #if FID_STATS
608 tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
609 tslf, res, _claimed);
610 #endif
611 return res;
612 }
613 }
614
615 bool FreeIdSet::claim_perm_id(int i) {
616 assert(0 <= i && i < _sz, "Out of range.");
617 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
618 int prev = end_of_list;
619 int cur = _hd;
620 while (cur != end_of_list) {
621 if (cur == i) {
622 if (prev == end_of_list) {
623 _hd = _ids[cur];
624 } else {
625 _ids[prev] = _ids[cur];
626 }
627 _ids[cur] = claimed;
628 _claimed++;
629 return true;
630 } else {
631 prev = cur;
632 cur = _ids[cur];
633 }
634 }
635 return false;
636
637 }
638
639 void FreeIdSet::release_par_id(int id) {
640 MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
641 assert(_ids[id] == claimed, "Precondition.");
642 _ids[id] = _hd;
643 _hd = id;
644 _claimed--;
645 #if FID_STATS
646 tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
647 thr_self(), id, _waiters, _claimed);
648 #endif
649 if (_waiters > 0)
650 // Notify all would be safer, but this is OK, right?
651 _mon->notify_all();
652 }